In the wind industry, the current trend is towards building larger and larger
turbines. This presents additional structural challenges and requires blade materials that
are both lighter and stiffer than the ones presently used. This work is aimed to aid the
work of designing new wind turbine blades by providing a comparative study of different
composite materials.
A coupled Finite-Element-Method (FEM) - Blade Element Momentum (BEM) code was
used to simulate the aerodynamic forces subjected on the blade. The developed BEM
code was written using LabView allowing an iterative numerical approach solver taking
into the consideration the unsteady aerodynamic effects and off –design performance
issues such as Tip Loss, Hub Loss and Turbulent Wake State therefore developing a more
rational aerodynamic model. For this thesis, the finite element study was conducted on
the Static Structural Workbench of ANSYS, as for the geometry of the blade it was
imported from a previous study prepared by Cornell University. Confirmation of the
performance analysis of the chosen wind turbine blade are presented and discussed blade
including the generated power, tip deflection, thrust and tangential force for a steady flow
of 8m/s.
The elastic and ultimate strength properties were provided by Hallal et al. The Tsai-
Hill and Hoffman failure criterions were both conducted to the resulting stresses and
shears for each blade composite material structure to determine the presence of static
rupture. A progressive fatigue damage model was conducted to simulate the fatigue
behavior of laminated composite materials, an algorithm developed by Shokrieh.
It is concluded that with respect to a material blade design cycle, the coupling between a
finite element package and blade element and momentum code under steady and static
conditions can be useful. Especially when an integration between this coupled approach
and a dynamic simulation tool could be established, a more advanced flexible blade
design can be then analyzed for a novel generation of more flexible wind turbine blades.
Table of Contents
CHAPTER I: Literature Review
1.1 Background
1.2 Scopes and Aims
CHAPTER II: Aerodynamic Modeling
2.1 Methods for Calculating Aerodynamic Forces
2.2 BEM Model
2.2.1 Introduction
2.2.2 BEM Theory
2.2.3 Correction Models
CHAPTER III: Structural Modeling
3.1 Blade Design
3.2 Blade Model
3.3 Load Application
3.3.1 Chord Length, Aerodynamic Centre and Twist Angle
3.3.2 Load Application and Moment Correction
3.4 Material Elastic Properties
3.5 Static Failure Criteria’s
CHAPTER IV: Results
4.1 Static Failure: Interlock Textures
4.2 Static Failure: Orthogonal Laminates
4.3 Static Failure: Braded Textures
CHAPTER V: Fatigue Model
5.1 Overview
5.2 Progressive Fatigue Damage Model
CONCLUSION & FUTURE WORK
Objectives and Research Themes
The primary objective of this research is to conduct a comparative study of different composite material structures for wind turbine blades, specifically focusing on their static and fatigue behaviors under aerodynamic loads, in order to facilitate the design of lighter and more flexible turbine blades.
- Coupled Finite Element Method (FEM) and Blade Element Momentum (BEM) aerodynamic modeling.
- Comparative analysis of static failure performance for various composite textures (interlock, orthogonal, and braided).
- Development of a progressive fatigue damage model for laminated composite materials.
- Evaluation of material elastic properties and failure criteria under operational conditions.
Excerpt from the Book
3.2 Blade Model
To create the structural model of the blade, a finite element approach using the static structural workbench of ANSYS was used. A hexahedral element meshing with a 0.1 m size allowed the decomposition of the blade into 14770 nodes and 15103 elements. A zero total deformation at the hub was assumed as a constraint and hence the blade is assumed a cantilever beam attached to a rotating ring (see figure 3.3).
Summary of Chapters
CHAPTER I: Literature Review: This chapter provides the theoretical background on wind turbine blade design and outlines the scope and aims of the study, emphasizing the shift towards lighter and more flexible blades.
CHAPTER II: Aerodynamic Modeling: This section details the Blade Element Momentum (BEM) theory and numerical methods used to calculate aerodynamic forces acting on the turbine blades, including necessary correction models.
CHAPTER III: Structural Modeling: This chapter focuses on the geometric modeling of the blade, load application strategies, and the implementation of static failure criteria to assess material integrity.
CHAPTER IV: Results: This chapter presents the comparative static failure analysis results for interlock, orthogonal, and braided composite textures using Tsai-Hill and Hoffman criteria.
CHAPTER V: Fatigue Model: This chapter introduces a new progressive fatigue damage model designed to predict the fatigue life of composite laminates based on regional elements and material degradation.
CONCLUSION & FUTURE WORK: This chapter synthesizes the research findings, confirming the effectiveness of the coupled FEM-BEM approach and suggesting future research directions.
Keywords
wind turbine blade, BEM, FEM, aerodynamic, orthotropic, static, fatigue, composite materials, structural modeling, failure criteria, progressive damage model, blade design, finite element analysis, material degradation, structural behavior.
Frequently Asked Questions
What is the core focus of this research?
This thesis examines the static and fatigue behavior of various orthotropic composite materials used in wind turbine blades to support the design of lighter, more efficient components.
Which scientific methodology is employed?
The author uses a coupled FEM-BEM approach, combining Blade Element Momentum theory for aerodynamics with Finite Element Method analysis for structural performance.
What are the primary material types analyzed?
The study investigates various textures including interlock, orthogonal, and braided composites to compare their performance under load.
What is the goal of the fatigue modeling in this work?
The aim is to develop a progressive fatigue damage model that considers material property degradation to predict the lifespan of composite structures under multiaxial fatigue loading.
How is the structural load applied in the simulations?
Loads are applied by discretizing aerodynamic forces onto the nodal points of the blade model, accounting for chord length, aerodynamic center, and twist angle.
Why are correction models like the Glauert correction used?
These models are necessary to adjust the BEM theory when standard assumptions fail, particularly under high-load conditions or when the rotor enters the turbulent wake state.
What do the Tsai-Hill and Hoffman criteria indicate?
These are failure theories used to predict whether a specific composite material will reach static rupture under defined aerodynamic stresses.
Which composite texture demonstrated the best static performance?
The study found that the LTL1 laminate composite exhibited the highest degree of safety among the tested materials.
How does the research address the complexity of material degradation?
It uses both sudden and gradual material property degradation rules to simulate the damage accumulation process in the fatigue model.
What are the practical applications of this modeling?
The findings serve as a decision-support tool for engineers to evaluate the pros and cons of different composite materials during the wind turbine blade design cycle.
- Citation du texte
- Adam Chehouri (Auteur), 2013, A Comparative Study of Static and Fatigue Behaviors for Various Composite Orthotropic Properties for a Wind Turbine Using a Coupled FEM-BEM Method, Munich, GRIN Verlag, https://www.grin.com/document/267156
